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GCN Circular 21033

Subject
GRB 170424A: Fermi GBM detection
Date
2017-04-25T01:05:33Z (7 years ago)
From
Matthew Stanbro at UAH/Fermi <mcs0001@uah.edu>
M. Stanbro (UAH), A. von Kienlin (MPE) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 10:12:30.75 UT on 24 April 2017, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 170424A (trigger 514721555 / 170424425)
which was also detected by the Fermi-LAT (N. Omodei et al. 2017, GCN 21032).
The GBM on-ground location is consistent with the Fermi-LAT position.

 This burst was also independently detected by INTEGRAL SPI-ACS.

The GBM light curve consists of one episode
with a duration (T90) of about 52 s (50-300 keV).
The time-averaged spectrum from T0+1.54 s to T0+55.81 s is
best fit by a Band function with Epeak = 464 +/- 39 keV,
alpha = -0.85 +/- 0.03, and beta = -2.00 +/- 0.09.

The event fluence (10-1000 keV) in this time interval is
(3.07 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+23.5 s in the 10-1000 keV band
is 4.8 +/- 0.2 ph/s/cm^2.

A power law function with an exponential
high-energy cutoff fits the spectrum equally well.
The power law index is -0.89 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 570 +/- 33 keV.


The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
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